1. Field of the Invention
This invention relates to a light-intercepting blade which is required to move at a high speed, such as the shutter blades or the diaphragm blades of the focal plane shutter or the lens shutter of a camera.
2. Description of the Prior Art
Focal plane shutter blades are required to move at a high speed to secure the simultaneity of the exposures in the various portions of the photographing picture plane, and a diaphragm blades is required to move at a high speed to reduce the rate of the stop-down time in the time required for the photographing sequence of the camera. As a method for realizing high-speed movement of the light-intercepting blade, it would occur to mind to increase the amount of operating force, but this would increase the energy required for the operation for storing the amount of force and, in case of manual operation, would give the sense of displeasure to the operator and, in case of electric operation, would increase the power consumption of the motor.
Further, in this method, the shock force applied to the blade itself at the start or end of the movement is great and thus, this method is disadvantageous in durability as well.
As another method, it would occur to mind to reduce the weight of the light-intercepting blade. However, there is a limit in reducing the thickness of the blade because mechanical strength such as rigidity necessary as a light-intercepting blade must be maintained and the planarity of the blade must be secured. For this reason, it has been attempted to reduce the weight of the blade by partly thinning the surface of the blade instead of thinning the entire blade. In this case, however, the surface of the blade is uneven and this is liable to cause a concentrated stress. Also, where several such blades are used to form a shutter, there is a danger that light may leak in the portion wherein the blades overlap each other. To eliminate these disadvantages, special contrivance is required in the combination and overlapping of the blades, and this is turn renders design and manufacture combersome.